High prevalence of depression (25%-45%) among individuals with dementia and the associated worsening of a wide array of negative outcomes warrants research to evaluate the effectiveness of depression treatment among individuals with dementia. To the best of our knowledge, no study to date has been conducted to evaluate depression treatment outcomes among older adults with dementia in real world situations. Our proposed study will be the first of its kind study to use a large nationally representative sample of older adults with dementia to assess the adherence to and outcomes associated with the Healthcare Effectiveness Data and Information Set (HEDIS) antidepressant medication management (AMM) measures. Our long-term objective is to provide real-world evidence for healthcare providers, patients and caregivers, who can make informed decisions to prioritize treatment for depression, which is especially important to maintain functional independence and improve quality of life among individuals with dementia. To accomplish this objective, we propose three specific aims - (Aim 1): Quantify the extent and identify predictors of inappropriate antidepressant use among older adults with dementia newly diagnosed with major depression. (Aim 2): Determine the degree and predictors of adherence to the HEDIS AMM measures in acute and continuation phase treatment among older adults with dementia and newly diagnosed major depression. (Aim 3): Examine health outcomes and expenditures associated with adherence to HEDIS AMM measures during acute and continuation phases of depression treatment among older adults with dementia newly diagnosed with major depression. We will use a retrospective longitudinal cohort study design with Medicare 5% sample claims data (2011-2013) for the purpose of this study. The study population will consist of older adults (age ? 65 years) with dementia newly diagnosed with major depression. Depression treatment will be identified using the HEDIS depression treatment recommendation for effective AMM during acute (at least 84 days of antidepressant use during the first 115 days of treatment initiation) and continuation (at least 180 days of antidepressant use during the first 232 days of treatment initiation) phase treatment post new major depression diagnosis. We will achieve the study aims by using a robust study design (Inverse Probability of Treatment Weighting) and applying advanced statistical techniques such as multi-level modeling, Cox Proportional Hazards regression and Generalized Linear Model with log-link and gamma distribution. Apart from providing real-world evidence of effectiveness of depression treatment, our findings also have the potential to significantly influence revisions of the existing HEDIS AMM measures to be adapted for treating depression among older adults with dementia.